Grinder with automatic compensation for wheel dress



Sept. 5, 1967 c. E. CLELAND GRINDER WiTH AUTOMATIC COMPENSATION FOR WHEEL DRESS 5 Sheets-Sheet 1 Filed March 29, 1965 hirlagfl la /and GRINDER WITH AUTOMATIC COMPENSATION FOR WHEEL DRESS Filed March 29, 1965 v .c. .E. CLELAND Sept. 5, 1967 5 Sheets-Sheet 2 RESERVOI Q Sept. 5, 1967 c. E. CLELAND GRINDER WITH AUTOMATIC COMPENSATION FOR WHEEL DRESS Filed March 29, 1965 3' Sheets-Sheet 5 Mar/35E 5/1 /5270 (Q, I

United States Patent 3,339,317 GRINDER WITH AUTOMATIC COMPENSATION FOR WHEEL DRESS Charles E. Cleland, Minneapolis, Minn., assignor to Continental Machines, Inc., Savage, Minn., a corporation of Minnesota Filed Mar. 29, 1965, Ser. No. 443,552 12 Claims. (Cl. 51-165) ABSTRACT OF THE DISCLOSURE The radius of the grinding wheel of a surface grinder is reduced the same fixed amount each time the wheel is dressed, and the downfeed compensating motion of the wheel is not only dependent upon completion of each dressing cycle but is constrained to an amount of motion exactly equal to the reduction in grinding wheel radius.

This invention relates to grinders, and has more particular reference to precision surface grinding machines of the type wherein grinding to extremely close tolerances compels periodic dressing of the grinding wheel to true its periphery.

Such dressing of the grinding wheel may be effected just prior to the final finishing pass, by moving a diamond dressing tool into dressing engagement with the periphery of the wheel. This is ordinarily accomplished after the reciprocat-ory motion of the work supporting table has been stopped, usually at one limit of its travel, and after the final cross feed indexing of the table has carried the workpiece thereon entirely to one axial side of the grinding wheel.

Since the dressing operation reduces the radius of the grinding wheel, the normal amount of down feed motion imparted to the grinding wheel just before the final finish ing pass is commenced must always be increased by an amount exactly equal to the reduction in wheel radius in order to compensate for the dressing operation. Such compensation can be effected manually, by rotating the down feed hand wheel to turn the lead screw supporting the head or column of the grinder in the proper direction. This was highly objectionable for the reason that the dimensional down feed reference scale located on the periphery of the hand wheel was then also turned, so that the down feed scale was thenceforth erroneous by whatever amount the hand wheel was turned to compensate for the dressing reduction in wheel radius.

It is one of the purposes of this invention, therefore, to provide exceptionally simple drive means for effecting down feed compensating motion of the grinding wheel any desired and precise amount, without entailing rotation of the lead screw supporting the head or colum on which the grinding wheel is mounted and, of course, without disturbing the down feed scale on the hand wheel controlling rotation of the lead screw.

In the past, it was also customary to leave to the discretion of the operator of the machine the amount of grinding wheel to be removed during each dressing operation. This necessitated employment of expensive and complicated position measuring systems comprising Selsyn units or the like in order to match the amount of down feed compensation to the reduction in wheel radius.

In this respect, it is a most important purpose of this invention to provide means for adjustably presetting and fixing the amount of material removed from the grinding wheel during each dressing operation, so that the radius of the wheel will always be reduced the same amount each time the wheel is dressed, and so that the amount of down feed compensation of the grinding wheel can be set to correspond exactly to this reduction in wheel radius.

More specifically, it is a purpose of this invention to provide means for automatically indexing the dressing tool toward the axis of the grinding wheel a predeterminable and fixed amount as a consequence of operation of actuating means for effecting wheel dressing movement of the tool relative to the periphery of the grinding wheel, and to also coordinate the operation of said tool actuating means with operation of the drive means by which down feed compensation is effected so as to assure against down feed compensation taking place without dressing of the grinding wheel.

With these and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and inwhich:

FIGURE 1 is a perspective view of a precision surface grinding machine embodying this invention;

FIGURE 2 is a view diagrammatically illustrating the essential components of this invention along with control means for governing their operation;

FIGURE 3 is a view taken on line 33 in FIGURE 2 and illustrating details of the indexing mechanism for the diamond dressing tool; and

FIGURE 4 is a view illustrating details of the drive means for effecting down feed compensation of the grinding wheel.

Referring now to the accompanying drawings, the numeral 10 designates the grinding wheel of a more or less conventional precision surface grinder of the type having a vertically movable column or head 11 to support the wheel, and its drive motor 12, for rotation on a horizontal axis above a work supporting table or carriage 13. A base 14 supports the head or column 11 for vertical translatory motion along ways (not shown) at the back of the machine, so that the grinding wheel 10 can be fed toward and moved away from a workpiece W on the table. A conventional magnetic chuck (not shown) can serve to hold the workpiece in position on the table.

As is customary, the table 13 is mounted on a saddle 15 for horizontal reciprocatory motion relative thereto along a path normal to the axis of the grinding wheel, and the saddle in turn, is mounted for in and out cross feed motion on the base 14, to carry the table along a path parallel to the axis of the wheel. Hence, the table can be moved in the directions necessary to present all portions of the top surface of, the workpiece thereon to the grinding wheel 10.

The work supporting table or carriage 13 is reciprocated in a known manner by means including an automatically controlled double acting fluid pressure operated motor 16 such as the hydraulic cylinder indicated in FIGURE 2; and conventional fluid pressure operated drive mechanism (not shown) is connected to the saddle to impart cross feed indexing motion thereto as the table reaches one of its limits of reciprocating motion.

As is customary, the spatial relationship between the grinding wheel 10 and the work supporting table 13 therebeneath is determined by the axial position of a vertically disposed lead screw 17 relative to the base. The upper end of the lead screw 17 is supportingly connected with the head or column in a manner allowing the screw to rotate relative thereto, and its lower end portion is engaged in anut 18 carried by the base 14. Consequently,

3 rotation of the lead screw in one direction relative to the nut causes the head and the grinding wheel thereon to be lifted, while rotation of the lead screw in the opposite direction relative to the nut 18 causes the head and grinding wheel to descend toward the workpiece.

During grinding of the surface of a workpiece W, the operator of the machine can rotate the lead screw to lower the head at the completion of a grinding pass, in order to adjust the grinding wheel in the work feeding direction for the next grinding pass. The amount of such down feed motion of the grinding wheel must be capable of very accurate control, and is ordinarily measured on a scale carried by the down feed hand wheel 20 through which the lead screw is turned. The hand wheel is drivingly connected to the lead screw by means of a worm 21 on the handwheel shaft, meshing with a worm wheel 22 fixed on the upper end of the lead screw. Those skilled in the art will appreciate that such down feed motion of the grinding wheel can also be effected automatically.

Mounted on the head or column 11 to move up and down therewith is a wheel dressing assembly, generally designated 24. This assembly comprises an upright tubular body 25, a tool holder 26 which is movable up and down in the body in consequence of rotation of a spindle 27 having a coaxial threaded connection (not shown) with the tool holder, and a diamond dressing tool 28 removably carried by the tool holder. The dressing tool 28 projects from the bottom of the body for engagement With the periphery of the grinding wheel 10, and the spindle 27 projects upwardly out of the body and through a ratchet housing 29 to have a manually actuatable adjusting knob 30 affixed thereto.

The assembly 24 is mounted on the head or column 11, above the grinding wheel, by means of a rigid slide 31 fixed to the body 25 and extending horizontally from one side thereof into a bearing 32 on the head, having a bore 33 to snugly but slidably receive the slide. The axis of the bore 33 is parallel to that of the grinding wheel, and both axes lie in a common vertical plane. Since the slide 32 must be held against rotation in its hearing, it is preferably non-circular in cross section, as for instance, square, and the bore 33 has wall surfaces corresponding to the shape of the exterior of the slide.

The bearing 32 thus mounts the wheel dressing assembly for reciprocatory movement to enable the dressing tool to be carried from a normal or rest position near one face of the grinding wheel, across its periphery and beyond the opposite face of the wheel, and for return movement to its normal position. Such reciprocatory movement is imparted to the wheel dressing assembly by means of a double acting fluid pressure operated cylinder 35 connected to the bearing 32 at its end remote from the dressing tool, and having its piston rod 36 operatively connected to the slide 31 as at 37.

From the description thus far, it will be apparent that the diamond dressing tool will effect dressing and truing of the grinding wheel during traversal thereof across the periphery of the wheel, provided the diamond point on the tool has been indexed toward the wheel axis to a position spaced therefrom a distance slightly less than the maximum radius of the wheel. In practice, for example, the diamond dressing tool may be indexed toward the wheel axis by as much as .0005 inch each time the wheel is dressed. This indexing of the tool may be effected manually by rotation of the knob 30, but this invention provides motion producing means 40 which effects indexing of the dressing tool a predeterminable and fixed amount each time wheel dressing movement is imparted to the dressing assembly 24 by its operating cylinder 35.

The motion producing means 40 is of the pawl and ratchet type. The ratchet 42 is fixed to the spindle 27 and is confined within the housing 29, which more or less freely rotatably encircles the upper end portion of the spindle and the upwardly extending hub 44 of the ratchet.

The housing rests upon a stop collar 45 which surrounds the spindle 27 and is fixed to and closes the upper end of the tubular body 25. The housing comprises upper and lower housing sections 46 and 47 respectively, which are held in place enclosing the ratchet disc and the pawl 48 by a plurality of bolts 49.

The pawl 48 is received in a radial slot 50 in the lower housing section 47, to slide toward and from the teeth 51 on the periphery of the ratchet, and a compression spring 52 confined between the outer end of the pawl and the side wall of the housing yieldingly urges the pawl inwardly toward a normally operaitve position at which its inner end is received between two adjacent teeth 51 of the ratchet.

A pawl disabling member 53 slidably carried by the ratchet housing, can be provided to hold the pawl in an inoperative position disengaged from the ratchet teeth, to enable the dressing tool to be freely manually adjusted by the knob 30. With the teeth of the ratchet oriented as seen in FIGURE 3, the housing 29 can be rocked in the clockwise direction about the axis of the spindle 27 to impart rotation to the spindle in the same direction, through the pawl and ratchet connection between the housing and spindle. Such rotation of the spindle results in downward indexing motion of the diamond dressing tool an extent determined by the magnitude of the angle through which the housing is rocked.

It is one of the main features of this invention that the housing can always be rocked in the clockwise direction through the same angle whenever the dressing assembly is retracted following each wheel dressing operation; for example, to advance the ratchet by one tooth, and thereby index the dressing tool a fixed amount toward the axis of the grinding wheel. The amount of indexing motion thus imparted to the dressing tool may be on the order of .0005 inch, so as to reduce the diameter of the grinding wheel by .001 inch with each dressing operation.

Such clockwise rocking motion of the housing is effected during return motion of the dressing assembly, to the left as seen in FIGURE 3, in consequence of the engagement of one of end portion of a stop bar 54 suitably afi'ixed to the underside of the housing, with an adjustable stop in the form of a screw 55 carried by a standard 56 on the bearing 32. A tension spring 57 connected between a lug 58 on the stop collar 45 and the opposite end of the stop bar serves to bias the housing in the counter-clockwise direction of rotation. The spring 57, of course, rocks the housing in the counterclockwise direction during initial wheel dressing movement of the dressing assembly out of its normal position, to re-engage the pawl in the next tooth space on the ratchet. The stop bar engages the outer end of a pin 59 on the lug 58 of the stop collar to limit counter-clockwise rocking motion of the housing to an angle equal to the pitch of the ratchet teeth.

Hence it will be seen that the hydraulic cylinder 35, which always returns the dressing assembly to the same position following dressing of the grinding wheel, cooperates with the two stops 55 and 59 to always advance the ratchet by one tooth, and correspondingly index the dressing tool the same fixed amount toward the axis of the grinding wheel each time the wheel is dressed. It will be appreciated, however, that whenever grinding conditions require indexing of the dressing tool a greater amount, the stop 55 can be adjusted toward the dressing assembly so as to effect advance of the ratchet by two teeth, or more, each time the dressing operation is concluded.

If desired, the stop collar 45 can incorporate braking means (not shown) for the spindle 27, to prevent it from turning during pawl resetting or counterclockwise motion of the ratchet housing.

It is also a feature of this invention to provide for feeding of the grinding wheel downwardly an amount exactly equal to the amount the dressing tool is indexed with each dressing operation on the wheel. This feature is achieved through the provision of compensating means carried by the base and .generally designated 65. The nut 18 on the lead screw 17 is one of the components of this compensating means. It is rotatably journaled in a bearing '66 fixed to the base, with upper and lower ends projecting from the bearing. A thrust washer 67 encircles the upper end portion of the nut and is interposed between the adjacent end of the bearing 66 and a circumferential .flange or head 68 on the exterior of the nut. A worm gear 69 is fixed to the lower end of the nut, and a second thrust washer 70 is interposed between the gear and the lower end of the bearing 66. Hence, the head 68 and worm gear 69 cooperate with the bearing 66 to prevent movement of the nut lengthwise of the lead screw.

Inasmuch as the worm drive 21-22 prevents rotation of the lead screw except by the hand wheel 20, the nut can be rotated relative to the lead screw to cause the screw to be lowered bodily relative to the base, to thus effect whatever downward adjustment of the grinding wheel is necessary to compensate for dressing of the grinding wheel. It is noteworthy that this downward compensating motion of the grinding wheel can be effected without turning the down feed hand wheel 20. Consequently, the hand wheel scale will not be disturbed by nut-produced downward compensating motion of the grinding wheel, and if :down feed motion is effected manually, the scale will accurately indicate to the operator the amount of down feed adjustment he desires to make while turning the hand wheel after each grinding pass across the work surface. 1

According to this invention, instrumentalities which can function only when a dressing operation is performed on the grinding wheel, act through the nut 18 to effect downward compensating motion of the grinding wheel an amount exactly equal to that which the dressing tool is indexed toward the Wheel axis each time the wheel is dressed. These instrumentalities include the worm gear 69 on the bottom of the nut 18, a worm 72 fixed on a horizontally disposed worm shaft 73 and meshing with the gear 69, a pinion 74 on the worm shaft, a rack v75 having teeth meshing with those of the pinion, and a double acting hydraulic cylinder 76 having its piston rod 77 connected to one end of the rack as at 78.

The cylinder 76 is fixed to a bracket assembly 79 on the base of the machine with its axis horizontal, crosswise of and slightly below the axis of the worm shaft, and so that its piston rod can reciprocate the rack 75 back and forth beneath the pinion 74. The worm shaft is rotatably supported at one end in a bearing plane 80 on the nut bearing 66, and at its other end in a second bearing 81 carried by the base.

The pinion 74, when rotated in the counterclockwise direction as seen in FIGURE 4, drives the worm shaft 73 and the nut 18 in the direction to effect lowering of the lead screw and hence the grinding wheel 10. Such rotation is imparted to the pinion by the rack 75 whenever the piston rod 77 of the hydraulic cylinder is extended. During the retraction stroke of the piston rod, the pinion rotates freely in the clockwise direction relative to the worm shaft, due to the incorporation of an overrunning or oneway clutch mechanism, generally designated 83, in the interior of the pinion. This clutch mechanism, of course, connects the worm shaft 73 with the pinion only during counterclockwise rotation of the pinion through its driving connection with the rack 75, and is of the type which establishes the desired drive with a very minimum or no lost motion in the driving connection between the pinion and worm shaft.

This invention also provides means to adjustably limit the extension stroke of the piston rod 77 and stop the same as soon as the amount the grinding wheel is lowered exactly matches and compensates for the dressing operation on the grinding wheel. For this purpose, a stop arm 85 is medially rockably received on the end of the worm shaft outwardly adjacent to the pinion 74. It has a lug 86 on its upper end overlying the toothed periphery of the pinion 74, and the lower end of a thumb screw 87 threaded into the lug can be engaged between any two adjacent teeth on the pinion to drivingly connect the arm therewith, with the arm in different angular positions relative to the pinion.

The lower end of the arm is provided with an abutment 88 which is adapted to engage the end of a fine adjustment screw 89 on the bracket assembly 79 to prevent counterclockwise rotation of the pinion beyond the degree necessary to match compensating down feed of the grinding wheel with the extent of radial indexing motion of the dressing tool.

From this it will be seen that the thumb screw 87 provides for course adjustment of the angle through which the worm shaft 73 will be driven by the pinion 74, in increments equal to the pitch of the teeth on the pinion, while the screw 89 provides for very fine adjustment of that angle at any setting of the screw 87. As shown by way of example, the arm 85 will stop the extending motion of the rack and piston rod after counter-clockwise rotation of the pinion through an angle of about 45 If, for example, the pawl and ratchet operated indexing mechanism for the dressing tool is adjusted to cause the tool to be indexed radially toward the grinding wheel axis a distance corresponding to a two tooth advance of the ratchet each time the dressing assembly is returned to its normal position, then the stop arm 85 would be correspondingly adjusted in the clockwise direction to a new position at which fine adjustment of the screw 89 would cause the grinding wheel to be lowered a correspondingly greater amount exactly matching the greater amount removed from the grinding wheel by the dressing tool.

An important feature of this invention resides in the provision of control means which functions in such a manner that dressing of the grinding wheel is a prerequisite to operation of the down feed compensating means 65, whereby down feed compensation can never be effected alone. One way of assuring this .desired result is to have the control means so coordinate the operation of the hydraulic cylinders 35 and 76 for actuation of the dressing assembly and compensating means, that compensation depends upon actuation of the dressing cylinder 35.

The control means shown in the FIGURE 2 diagram achieves this purpose by effecting simultaneous operation of the cylinders 35 and 76. As therein seen, a motor driven pump 90 draws hydraulic fluid from a reservoir 91 and delivers fluid under pressure to the cylinders 35 and 76 through a solenoid operated control valve 92 having its inlet connected with the outlet of the pump through a supply line 93. The valve has a first service line 94 connecting with the rod end of each of the cylinders 35 and 76, and a second service line 95 connecting with the head end of each of said cylinders. A spool 96 in the valve selectively controls communication between the supply line 93 and either service line, and is biased to a first operative position by a spring 97, to direct pressure fluid from the pump into the rod ends of both cylinders 35 and 76 and normally hold their piston rods in fully retracted positions.

The spool 96 is shifted to its second operating position upon energization of the solenoid 98 of the valve, against spring bias, to direct pressure fluid from the pump into the head ends of both cylinders. Hence, the control valve 92 provides a common control instrumentality for assuring that the piston rods of both cylinders will be simultaneously retracted, in the position of the valve seen in FIG- URE 2, and will be simultaneously advanced when the solenoid 98 is energized to shift the valve spool to its second operating position.

A surface grinding machine of this invention having automatically operated down feed and cross feed mechanisrns, not shown, can be provided with electrically conand 76. These cylinders preferably should be actuated at the completion of a grinding pass, while the table is held at one limit of its reciprocatory motion and the grinding wheel is wholly beyond the workpiece W. Counting mechanism 100 can be provided for this purpose. This counting mechanism is a conventional instrumentality that can be used to count some repeated function of the machine, such as each increment of automatically produced cross feed indexing motion of the saddle upon which the work table is mounted, or each increment of automatically produced down feed motion of the head to bring the grinding wheel closer to the surface of the work table at the end of each grinding pass. Thus, the counting mechanism may be preset to initiate actuation of the wheel dressing and compensating cylinders 35 and 76, for example, just before the final grinding pass, as a consequence of the head and grinding wheel having been indexed in the down feed direction a predetermined number of times. It does so through closure of an electric switch 101.

The closure of the switch 101 in this manner connects the coil 102 of an electromagnetic switch 103 across a pair of power lines L1L2 through conductors 104, 105 and 106. Conductor 104 connects with line L1 and leads through the switch 101 to the conductor 105, which connects with one side of the coil 102. The other side of the coil connects with line L2 through the conductor 106. As soon as switch 103 closes, its then bridged contacts 107 establish a holding circuit for the coil 102. This holding circuit leads from line L1 through a conductor 108 in which contacts 107 are located, to the conductor I105 connecting with one side of the coil 102, and through the coil to line L2 via conductor 106. As will be explained hereinafter, this holding circuit is maintained for as long as the contracts 109 of a time delay relay 110, in conductor 105, remain closed. For convenience, the contacts 109 of this time delay relay have been shown connected in series with the switch 101 of the counting mechanism, and the latter thus can be of the momentarily closed type with the circuitry described thus far.

A second set of contacts 111 is bridged by the switch 103 when its coil is energized in the manner described above, to set up a table blocking circuit that is adapted to stop the reciprocatory movement of the table at one of its limits of movement. This table blocking circuit is completed when a table actuated switch 112, connected in series with the contacts 111 of switch 103, is closed by the table at one end of the stroke of its operating cylinder 16 to effect energization of the solenoid 113 controlling a valve 114. The valve 114 governs the supply of hydraulic fluid to the cylinder 16, and blocks the supply to this cylinder when its coil 113 is energized, to stop the table.

The energizing circuit for the coil 113 leads through a conductor 115 connecting with line L1, serially through switch 112 and the now bridged contacts 111 of switch 103, to a conductor 116 connecting with one side of the coil 113. The other side of this coil is connected to line L2 by a conductor 117.

Simultaneously with energization of the coil of the table blocking valve 114 in this manner, the now closed switches 111 and 112 complete energizing circuits for the solenoid of the time delay relay 110, for the coil of a second time delay relay 118, and for the solenoid 98 of the control valve 92 governing the dressing and compensating cylinders 35 and 76. One end of the coil of the time delay relay 110 is connected to line L2, and its other end is connected by a conductor 119 with the conductors 116 and 115, which lead to line L1 through switch contacts 111 and switch 112.

The solenoid 98 of valve 92 and the coil of time delay relay 118, each have one end connected by a conductor 121 to line L2. Line L1 connects with the other end of coil 118 by means of the conductor 115 and a conductor 122 joined thereto, and line L1 is connected with the other end of the solenoid 98 of valve 92 by conductors 115 and 116 through the normally closed contacts 123 of time delay relay 118. Energization of the coils of time delay relays 110 and 118 as described does not result in opening of their respective contacts until after suitable time delay periods to be mentioned shortly.

When the solenoid 98 of control valve 92 is energized, however, the valve spool 96 is shifted to its second operating position, to the right as seen in FIGURE 2, to direct pressure fluid from the pump into the head end of each of the cylinders 35 and 76, to cause their piston rods to extend and start the wheel dressing and compensating operations. Fluid exhausting from the rod ends of these cylinders at this time is returned to the reservoir through the control valve, via the service line 94. Thus, while the dressing tool is moved across the periphery of the grinding wheel to dress and true the wheel, the compensating means will at the same time lower the grinding wheel the exact amount being removed from the wheel to compensate for such dressing thereof.

Shortly after completion of the actual dressing stroke of the cylinder 35, the time delay period of the relay 118 runs out, and its contacts 123 open to effect de-energization of the solenoid 98 of the control valve 92. When this occurs, the spring 97 returns the spool 96 of the valve to its normal position shown in the diagram, to direct pressure fluid from the pump into the rod ends of cylinders 35 and 76, via supply line 94, to retract the piston rods of these cylinders. Fluid exhausting from the head ends of the cylinders at this time is led back to the reservoir through the control valve, via supply line 95.

As the dressing assembly approaches its fully retracted position, the dressing tool is indexed its preset amount toward the axis of the grinding wheel, by the pawl and ratchet indexing mechanism described hereinbefore. Shortly thereafter, the delay period of relay runs out, and its contacts 109 open to break the holding circuit for the coil 102 of switch 103. Switch 103 then opens, to deenergize the coil 113 of the table blocking valve 114 and again render the cylinder 16 operative to reciprocate the work table. When switch 103 opens, of course, the energizing circuits for the coils of time delay relays 110 and 118 are disrupted, and the contacts 109 and 123 thereof reclose. The final grinding pass, with a freshly dressed and trued grinding wheel, is then underway.

It will be appreciated that, if desired, a manually operated switch can be used in place of the switch 101 of the counting mechanism, as a means of initiating operation of the dressing and compensating cylinders 35 and 76 whenever necessary or desired. In such cases, of course, the dressing and compensating operations would again be carried out with the grinding wheel disengaged from the work iece and the table at one limit of its reciprocatory travel. A manually operated switch of this type can also be connected in parallel with the counting switch 101, to enable extra dressing and compensating operations to be effected at non-scheduled intervals.

From the foregoing description, together with the accompanying drawings, it will be readily apparent that the surface grinder of this invention is unique in that it features wheel dressing instrumentalities that always remove a predeterminable but fixed amount from the periphery of the grinding wheel per dressing operation, so as to enable relatively simple mechanically operated means to 'be provided for effecting down feed compensation of the grinding wheel an exactly matching amount with each wheel dressing operation.

What is claimed as my invention is:

1. In a grinder having a work supporting table and a power driven grinding wheel mounted for relative movement toward and from one another to enable proper positioning of the periphery of the wheel with respect to a workpiece on the table:

(A) a dressing tool mounted for movement toward and from dressing engagement with the periphery of the grinding wheel and for indexing motion substantially radially toward the wheel axis;

(B) drive means connected with the dressing tool to move the same through a cycle of motion consisting of advance of the tool toward and into dressing engagement with the wheel and retraction of the tool following dressing of the wheel;

(C) means rendered effective in consequence of move ment of the tool through each cycle of motion to impart the same fixed amount of radial indexing motion to the tool, so as to cause the tool to reduce the radius of the grinding wheel the same amount each time the Wheel is dressed;

(D) other drive means for effecting relative motion between the grinding wheel and the table in the direc tion to bring the axis of the wheel closer to the surface of the table;

(E) means positively constraining the relative motion effected by said other drive means to an amount equal to said fixed amount of tool indexing motion;

(F) and means for preventing operation of said other drive means until said first designated drive means is openated to effect dressing of the grinding wheel.

2. In a surface grinder of the type wherein a work supporting table and a power driven grinding wheel are relatively bodily movable toward one another:

(A) a wheel dressing tool;

(B) means mounting the tool for wheel dressing movement relative to the periphery of the wheel and for indexing motion substantially radially toward the wheel axis;

(C) power means connected with the dressing tool and actuatable to impart said indexing and wheel dressing movements thereto, said power means including motion producing means to effect indexing of the tool the same pre-set increment in consequence of each actuation of said power means;

(D) power actuated compensating means associated with the table and the grinding wheel to effect relative movement thereof toward one another an extent exactly equal to said pre-set tool indexing increment; I

(E) and means for preventing operation of said power actuated compensating means until said first designated power means is actuated.

3. In a surface grinder of the type having a base, a work supporting table on the base, a head carried by the base and movable up and down relative thereto, and a rotatable grinding wheel carried by the head with its periphery above and facing the table:

(A) a tool for dressing the periphery of the wheel;

(B) means mounting the tool on the head for indexing movement substantially radially toward the wheel axis and for wheel dressing movement with respect to the periphery of the wheel;

(C) drive means connected with the dressing tool to effect said indexing and wheel dressing movements thereof, said drive means including motion producing means through which the drive means effects said indexing movement of the tool the same fixed amount each time the wheel is dressed;

'(D) drive means operatively connected with the head for imparting down feed compensating motion to the head to bring the periphery of the dressed grinding wheel closer to the Work supporting table;

(E) means positively constraining said down feed compensating motion imparted to the head by the'downfeed drive means to an amount equal to said fixed amount of indexing motion of the dressing tool;

(F) means to initiate operationof the drive means for the dressing tool;

(G) and means dependent upon operation of the drive means for the dressing tool to effect operation of said down feed drive means, whereby dressing of the grinding wheel by the dressing tool is a pre-requisite to down feed compensating motion of the head.

4. In a surface grinder of the type having a base mem- 10 her, a work supporting table on the base member, a head member carried by the base member for down feed motion relative thereto, and a rotatable grinding wheel carried by the head member with its periphery above and facing the table:

(A) means connected with the head member for imparting down feed motion thereto so as to bring the periphery of the grinding wheel closer to the work table, comprising (1) a rotatable lead screw operatively connected with one of said members,

(2) a rotatable nut on the lea-d screw,

(3) and means on the other of said members restraining the nut against axial movement relative to the lead screw, whereby down feed motion of the head member can be effected either by rotation of the nut relative to the screw or by rotation of the screw relative to the nut;

(B) a tool for dressing the periphery of the wheel;

(C) means mounting the tool on the head member for indexing movement substantially radially toward the wheel axis and for wheel dressing movement with respect to the periphery of the wheel;

(D) first drive means connected with the dressing tool to effect said indexing and wheel dressing movements thereof, said first drive means including motion producing means to effect said indexing movement of the tool the same fixed amount each time said first drive means is operated;

(E) second drive means connected with said nut to impart rotation thereto relative to the lead screw in the direction to effect down feed motion of the head member;

(F) means to constrain the rotation imparted to the nut by said second drive means each time the latter is operated, to an angle which produces an amount of down feed motion equal to said fixed amount of indexing movement of the dressing tool;

(G) means to effect operation of said first drive means;

(H) and means dependent upon operation of said first drive means to automatically effect operation of said second drive means.

5. The surface grinder of claim 4, wherein said means to effect operation of said first drive means effects concurrent operation of said second drive means.

6. In a grinder having work supporting means and a power driven grinding wheel arranged for relative movement toward and from one another to enable proper positioning of the grinding wheel relative to a workpiece on the work supporting means, means for dressing the periphery of the wheel and for adjusting its position relative to the work supporting means to retain a predetermined positional relationship between the periphery of the wheel and the workpiece and thereby compensate for the reduction in radius of the wheel caused by the dressing thereof, said means comprising:

(A) a dressing tool mounted for wheel dressing movement relative to the periphery of the wheel;

(B) means mounting the dressing tool for indexing motion substantially radially toward the axis of the grinding wheel;

(C) first power actuated motion producing means connected with the dressing tool, to impart wheel dressing movement thereto and to also impart indexing movement to the tool toward the axis of the grinding wheel the same fixed amount with each actuation of said motion producing means;

(D) second power actuated motion producing means connected with the grinding wheel, to effect relative motion between it and the work supporting means in the direction to bring the axis of the wheel closer to the surface of a workpiece being acted upon;

(E) means to constrain said relative motion of the grinding wheel and the work supporting means to an amount equal to said fixed amount of indexing motion of the dressing tool;

(F) means for activating said first power actuated motion producing means;

(G) and means dependent upon activation of said first power actuated motion producing means for activating the second power actuated motion producing means, whereby dressing of the grinding wheel is a prerequisite to relative motion of the Wheel and work supporting means toward one another to compensate for the amount removed from the grinding wheel with each dressing operation.

7. The grinder of claim 6, wherein said means for constraining the relative motion of the grinding wheel and the work support produced by the second power actuated motion producing means is adjustable; wherein a common power source is provided for said first and second power actuated means; and wherein common means provides for simultaneous connection of said first and second power actuated means with the power source.

8. In a surface grinder having a work supporting table and a grinding wheel mounted thereabove to rotate on an axis parallel to the plane of the table and perform its intended grinding operation upon a workpiece on the table with each relative traverse between the grinding wheel and the table providing the spacing between the periphery of the wheel and the table is correct;

(A) a wheel dressing tool;

(B) means mounting the dressing tool for traverse thereof across the periphery of the grinding wheel and for indexing adjustment substantially radially toward the wheel axis;

(C) first motion producing means operatively connected with the dressing tool to effect traverse thereof across the periphery of the grinding wheel and to also effect indexing movement of the tool the same fixed distance toward the wheel axis every time said first motion producing means is actuated;

(D) means mounting the grinding wheel and the table for relative motion perpendicular to the table so that the spacing between the table and the periphery ofthe wheel can be adjusted to compensate for reduc tion in wheel radius resulting from dressing of the wheel,

(E) second motion producing means for effecting relative motion of the grinding wheel and the table toward one another;

(F) means dependent upon operation of said first motion producing means for effecting operation of said second motion producing means;

(G) and means to constrain said relative motion of the grinding wheel and the table to an amount equal to said fixed distance the dressing tool is indexed with each dressing of the wheel.

9. In a surface grinder of the type wherein a work supporting table and a power driven grinding wheel are relatively bodily movable toward one another:

(A) a wheel dressing tool mounted for wheel dressing movement relative to the periphery of the grinding wheel and for indexing motion substantially radially toward the wheel axis;

(B) first hydraulic motor driven means connected with the dressing tool and operable to impart wheel dressing movement thereto;

(C) motion producing means actuated by said hydraulic motor driven means and operable to impart the same fixed amount of indexing motion to the dressing tool each time the wheel is dressed;

(D) second hydraulic motor dirven compensating means associated with the table and with the grinding wheel to effect relative movement thereof toward one another an extent exactly equal to said fixed amount of indexing motion of the dressing tool each time said second motor driven means is operated;

(E) and means for coordinating the operation of said first and second hydraulic motor driven means so as to assure operation of said hydraulic motor driven compensating means in dependence upon operation of said first hydraulic motor driven means.

10. The surface grinder of claim 9, wherein:

(A) the wheel dressing tool is mounted for wheel dressing motion toward and from the periphery of the grinding wheel, parallel to its axis of rotation;

(B) wherein said first hydraulic motor driven means comprises a hydraulic cylinder having a Work performing element connected with the dressing tool to move the same toward and from dressing engagement with the periphery of the grinding wheel;

(C) and wherein said motion producing means comprises:

(l) a ratchet drivingly connected with the dressing tool and operable upon rotary movement thereof through a predetermined angle in one direction to impart said fixed amount of indexing motion to the dressing tool,

(2) and a pawl actuated in consequence of operation of said cylinder, for rotating the ratchet through said predetermined angle, in said direction, each time the wheel is dressed.

11. In a grinder of the type having a grinder head including a grinding wheel rotatable on an axis fixed with respect to the head:

(A) a wheel dressing tool;

(B) means carried by the head mounting the tool (1) adjacent to the periphery of the grinding wheel,

(2) for indexing movement radially toward the wheel axis,

(3) and for wheel dressing movement relative to the periphery of the wheel;

(C) drive means having a movable motion transmitting member connected with the tool for imparting wheel dressing movement thereto;

(D) and tool indexing means connected with the tool and activated by the movement of said motion transmitting member of said drive means to effect indexing of the tool the same fixed amount toward the wheel axis each time the drive means is operated.

12. In a grinder of the type having a head and a grinding wheel carried thereby for rotation on an axis fixed with respect to the head, means for dressing the periphery of the grinding wheel, comprising:

(A) an assembly mounted on the head for back and forth movement parallel to the axis of the grinding wheel and across its periphery;

(B) drive means carried by the head and operatively connected with said assembly to impart said back and forth motion thereto;

(C) a wheel dressing tool carried by said assembly for engagement with the periphery of the wheel during movement of the assembly in one direction, to effect dressing of the wheel;

(D) means mounting the tool on the assembly for indexing motion radially toward the axis of the grinding wheel;

(E) and motion producing means activated by motion of said assembly in one direction for imparting the same fixed amount of said indexing motion to the dressing tool each time said drive means is operated to effect dressing of the grinding wheel.

References Cited UNITED STATES PATENTS 1,976,123 10/1934 Haas -11 2,127,877 8/1938 Maglott 51-92 3,157,969 11/1964 Fant et a1. 5ll65 LESTER M. SWINGLE, Primary Examiner. 

11. IN A GRINDER OF THE TYPE HAVING A GRINDER HEAD INCLUDING A GRINDING WHEEL ROTATABLE ON AN AXIS FIXED WITH RESPECT TO THE HEAD: (A) A WHEEL DRESSING TOOL; (B) MEANS CARRIED BY THE HEAD MOUNTING THE TOOL (1) ADJACENT TO THE PERIPHERY OF THE GRINDING WHEEL, (2) FOR INDEXING MOVEMENT RADIALLY TOWARD THE WHEEL AXIS, (3) AND FOR WHEEL DRESSING MOVEMENT RELATIVE TO THE PERIPHERY OF THE WHEEL; (C) DRIVE MEANS HAVING A MOVABLE MOTION TRANSMITTING MEMBER CONNECTED WITH THE TOOL FOR IMPARTING WHEEL DRESSING MOVEMENT THERETO; (D) AND TOOL INDEXING MEANS CONNECTED WITH THE TOOL AND ACTIVATED BY THE MOVEMENT OF SAID MOTION TRANSMITTING MEMBER OF SAID DRIVE MEANS TO EFFECT INDEXING OF THE TOOL THE SAME FIXED AMOUNT TOWARD THE WHEEL AXIS EACH TIME THE DRIVE MEANS IS OPERATED. 